1. Field of the Invention
This invention relates to an improved apparatus for conducting electroplating operations.
2. Description of the Prior Art
Electroplating is the electrodeposition of an adherent metallic coating upon an electrode for the purpose of securing a surface on the electrode having properties or dimensions different from those of the base metal. As such electroplating is a surface treatment. It has for its purpose the alteration of the surface properties of the work being treated, which is made the cathode in an electroplating solution or bath. Such baths are almost always aqueous solutions so that the metals which can be deposited are limited generally to those which are capable of being discharged from aqueous solutions of their salts.
It is usual to classify electroplating operations according to the principle functions of the deposited plate. Thus, the plating may be applied mainly for (1) appearance; (2) protection; (3) special surface properties; or (4) engineering or mechanical properties. These distinctions are not clear cut. A purely decorative plate may also to some extent at least serve to protect the base metal. One well known electroplating operation is the deposition of chromium or a chrome alloy on automobile parts, such as bumpers, to give a lustrous and shiny appearance. Not only does the chromium serve this decorative function but it also serves to protect the base metal of the part as well.
In conventional electroplating operations, the articles to be treated are usually first cleaned of undesirable surface deposits. This usually comprises dipping or soaking the articles in various types of cleaners and acids. After the article has been properly cleaned, the actual plate is applied by suspending the article in a plating tank having an appropriate aqueous solution therein. Temperature control is almost always desirable in the actual plating operation, because the characteristics of the plating solutions, of the final plating deposits, or of both usually depend to a large extent on the temperature of operation. Thus, many of the actual plating tanks have heating coils therein to maintain the temperature of the plating composition at a pre-determined ideal temperature. An important step in the operation involves thorough rinsing of the articles being treated. Adequate rinsing between all the steps in both the cleaning and the plating operations is usually of the utmost importance. It is known that hot water rinse is more efficient than cold.
It has been customary in prior electroplating systems that a linear arrangement of tanks be provided. In other words, the tanks containing the various cleaner and plating solutions have generally been arranged in a straight line. A work rack or the like then traverses the line from one end to the other with the work rack being dipped into each of the tanks. In such linear arrangements, one or more rinse tanks are located between each of the treating tanks to rinse the articles being treated as they pass down the line. Usually, these rinse tanks simply comprise a tank containing a large body of water in which the articles are dipped. Sometimes, the rinse tanks comprise a series of tanks which consecutively feed water into one another in a so-called cascade or counter-current arrangement. U.S. Patent No. 838,717 to Hutchinson shows a cascade rinse arrangement in which the rinse tanks are located between two adjacent rows of plating tanks A. U.S. Pat. No. 2,921,008 to Hauck et al discloses a conventional linear tank arrangement in a electroplating configuration. Barringer in U.S. Pat. No. 3,278,409 discloses a generally similar arrangement.
One problem with prior art linear tank arrays is the large number of rinse tanks which are required. This increases both the cost of providing suitable tanks and the amount of floor space needed for the electroplating apparatus. It further increases the amount of water needed to rinse the components. In addition, in a linear array, the speed of the articles moving down the line is often limited to the speed at which the slowest articles are moved. Thus, although some articles being treated in the line may not require lengthy immersion in each bath, other articles might require a lengthy immersion which correspondingly is imposed on all the articles in the line.
Another disadvantage with most prior art electroplating apparatuses is that relatively complex machinery is needed to lift and move the articles being treated between the treating tanks. For example, Ikeda, U.S. Pat. No. 3,887,094, discloses a trolley which can traverse over a rectangular array of tanks. However, the components comprising the trolley have to be quite strong, and thus expensive, because the hoisting apparatus for the work racks is also carried on the trolley. Thus, the trolley must be able to carry not only the weight of the work racks but also the weight of all the equipment associated therewith for hoisting the racks between an upper and lower position. Similarly, U.S. Pat. No. 3,699,983 to Morely discloses a traversable trolley or carriage device for moving up and down a linear array of tanks. Again, the hoisting apparatus for the work rack is carried on the trolley itself.
The Morley patent noted above attempts to do away with numerous rinse tanks by replacing all these tanks with a single rinsing zone. This rinsing zone is located at one end of a conventional linear tank array. Whenever it is necessary to rinse the article being treated, Morley discloses taking that article to the rinsing zone and submerging that article therein. Alternatively, Morley discloses showering the articles off in the rinsing zone. Similarly, the patent to Almegard, U.S. Pat. No. 3,734,108, attempts to do away with the many sprays or rinse tanks in a conventional linear arrangement by having a movable spray booth mounted above the treating tanks. This movable spray booth is moved to a position above the tanks containing the articles being treated. When it is desired to rinse these articles off, the articles are raised into the spray booth where they are rinsed off by a liquid spray.
Although Morley and Almegard alleviate somewhat the space problem occasioned by numerous in line rinse tanks, they have certain disadvantages. The apparatus of Almegard is extremely complex. This complexity makes it expensive which renders it somewhat impractical for use on a small scale. Similarly, although Morley used only a single rinsing zone, his rinsing zone is located at one end of an in line tank arrangement. To reach that particular rinse location, it is necessary to traverse the entire line when the article is located at the other end. This is time-consuming if the line is lengthy.